Providing Positional Awareness Information and Increasing Power Quality of Parallel Connected Inverters

ABSTRACT

A method and a system sense at least one phase difference between at least two phases of a group of parallel connected three phase AC output terminals (e.g., a first phase AC output terminal, a second phase AC output terminal, or a third phase AC output terminal). The parallel connected AC output terminals may be three parallel connected DC to AC three phase inverters. Features of the parallel connected three phase AC output terminals enable wiring of conductors to one phase of an AC output terminal to be swapped with wiring of conductors of one phase of another phase AC output terminal. A sign of at least one phase difference is verified different from signs of other phase differences thereby the system determining the lateral position of the at least one three phase inverters relative to at least one other of the three phase inverters.

RELATED APPLICATIONS

This application claims priority to U.S. provisional application Ser.No. 62/588,600, filed Nov. 20, 2017, entitled “APPARATUS AND METHOD TOPROVIDE POSITIONAL AWARENESS INFORMATION AND INCREASE POWER QUALITY OFPARALLEL CONNECTED INVERTERS.” The content of the foregoing applicationis incorporated by reference in its entirety.

BACKGROUND

Monitoring and control of power systems may provide for reliablefunctioning and maximum yield of any power system. The simplestmonitoring of a direct current (DC) to alternating current (AC) invertermay be performed by reading values on a display mounted on the housingof the inverter for example. Monitoring and control of the inverter maybe performed locally in close physical proximity to the inverter or by alocal wireless connection to the inverter. Monitoring and control of apower system and its components may also be done via a remote accessthrough an internet connection. Typical parameters to be monitored andcontrolled may include PV array voltages, currents and powers, utilitygrid voltages and currents. The parameters may be used to determineefficiency of power conversion from converters, for example, directcurrent (DC) to DC converters and DC to alternating current (AC)inverters.

SUMMARY

This summary merely presents some concepts in a simplified form as anintroductory prelude to the more detailed description provided below.This summary is not an extensive overview and is not intended to limitor constrain the detailed description or to delineate the scope of theclaims.

Illustrative aspects of the disclosure disclosed herein may be withrespect to a power system, the power system may include a controller,multiple power sources (e.g., DC power sources), multiple power devices(e.g., DC power devices such as DC to DC converters), multiplebi-directional power devices and multiple storage devices (e.g.batteries). Each of the power sources may be coupled to one or morepower device(s). The power devices outputs may be coupled in aconnection which may be a series connection of the power devicesoutputs, to form a serial string of power device outputs. The connectionmay also be a parallel connection of the power devices outputs. Theserial string or the parallel connection may be coupled to a load andmay also be coupled to the bi-directional power devices. Each of thebi-directional power devices may be coupled to respective storagedevices. Power of each of the power sources may be measured by sensorsof each of the power devices. The load may be multiple DC to ACinverters with outputs connected to a utility grid. The DC to ACinverter may be configurable to convert power from the grid (AC) to DCto supply the storage devices. The DC to AC inverter may be configurableto convert power from the power sources and/or storage devices to theload. More specifically, the inverters may be three phase inverters withAC outputs connected together such that power supplied to the load bythe inverters may be a combined power to the load. The connected outputsmay provide a first phase, a second phase and a third phase providedrespectively on a first phase AC output terminal, a second phase ACoutput terminal and a third phase AC output terminal. The first phase ACoutput terminal, the second phase AC output terminal and the third phaseAC output terminal may be provided in a junction box. The junction boxmay include a rail which may be utilized to mount DC circuit breakers,terminal blocks, an isolation switch and AC circuit breakers to provideprotection for the connected outputs supplying a load.

Illustrative aspects of the disclosure may feature two of the conductorsof the three phases of a three-phase output of at least one of the DC toAC three phase inverters being swapped and connected inside the junctionbox. Using the example of three DC to AC three phase inverters, aninstaller may mount and position the DC to AC three phase inverters toestablish one of the DC to AC three phase inverters is laterally to theleft or is laterally to the right of the other DC to AC three phaseinverters. In other words, the installer may establish a row ofinverters which may be designated as one inverter located laterally tothe left of a middle inverter and the junction box and another inverterlocated laterally to the right of a middle inverter and the junctionbox. The installer may perform a termination of the cables of theoutputs of the inverters in the junction box. The termination may besuch that all first phase AC outputs are connected to the first phaseterminal of the junction box (labeled as L1 for example). Thetermination may be that all the second phase AC outputs are connected tothe second phase terminal of the junction box (labeled as L2 forexample). The termination may be that all the third phase AC outputs areconnected to the third phase terminal of the junction box (labeled as L3for example).

Therefore, when the DC power on the pair of DC input terminals isconverted to a combined AC power on the first phase AC output terminal.The second phase AC output terminal and the third phase AC outputterminal, parameters may be sensed on the first phase AC outputterminal, the second phase AC output terminal or the third phase ACoutput terminal. The parameters may be voltage, current, frequency phaseangle, power factor, impedance, harmonic distortion or temperature. Byvirtue of two phases being swapped and connected inside the junctionbox, responsive to mounting of the row of inverters and the sensing ofthe parameters, it may become possible to verify the lateral positioningof the DC to AC three phase inverters to each other. The lateralpositioning of the DC to AC three phase inverters to each other may beutilized for mapping and identification labelling of the inverters inthe power system. As such the monitoring and/or sensing of the powersystem may allow the establishment of the power output of an identifiedinverter. The monitoring and/or sensing may establish the location ofthe identified inverter relative to other inverters. The monitoringand/or sensing may establish where a faulty inverter may be correctlylocated or that an inverter has been swapped, re-located or replacedwithout authorization.

In general, the lateral positioning of power devices (which may include,for example, DC to AC three phase inverters) to each other may beachieved by proximity sensors and respective targets located on each thehousings of the power devices. Proximity sensors and their targets maybe configurable to detect the presence of nearby power device toestablish the lateral positioning of the power devices to each other.Alternatively, the parameters sensed of a combined power output of aninverter from the first phase AC output terminal, the second phase ACoutput terminal or the third phase AC output terminal may be used in aconjunction with the use of proximity sensors and respective targets.The conjunction may be further used to obtain and/or verify the lateralpositions left (L) and right (R) of respective inverters relative to amiddle (M) inverter and the junction box.

Illustrative aspects of the disclosure may feature an auxiliary powerprovided to each of the DC to AC three phase inverters from the firstphase AC output terminal and a neutral terminal. The auxiliary power maybe provided from the second phase AC output terminal and the neutralterminal or the third phase AC output terminal and the neutral terminal.Connections in the junction box may draw the auxiliary power from theneutral (N) and inverter L1 terminals. Auxiliary power drawn may be byconnecting each L1 inverter terminal to a different phase of thecombined AC power terminated and provided in the junction box. The totalauxiliary power drawn by the inverters by virtue of the connection inthe junction box may be divided evenly among the phases of the combinedthree-phase AC output. The connection divided evenly among the phasesmay improve the load balancing and harmonic content of the combinedthree-phase AC output.

As noted above, this Summary is merely a summary of some of the featuresdescribed herein. It is not exhaustive, and it is not to be a limitationon the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood with regard to the followingdescription, claims, and drawings. The present disclosure is illustratedby way of example, and not limited by, the accompanying figures.

FIG. 1A illustrates a block diagram of a power system, according to oneor more illustrative aspects of the disclosure.

FIG. 1B illustrates a block diagram of a power system, according to oneor more illustrative aspects of the disclosure.

FIG. 1C illustrates details of wiring configurations shown in FIGS. 1Aand 1B, according to one or more illustrative aspects of the disclosure.

FIG. 1D illustrates circuitry which may be found in a power device,according to one or more illustrative aspects of the disclosure.

FIG. 1E illustrates a buck+boost circuit implementation for a powercircuit, according to one or more illustrative aspects of thedisclosure.

FIG. 1F shows a plan view of a physical layout for three system powerconverters, according to one or more illustrative aspects of thedisclosure.

FIG. 1G shows a part system block diagram and part schematic diagram forpower converter, according to one or more illustrative aspects of thedisclosure.

FIG. 2A shows a more detailed view of the inside contents included in ajunction box, according to one or more illustrative aspects of thedisclosure.

FIG. 2B shows a more detailed view of the AC three phase connectionsmade in a junction box, according to one or more illustrative aspects ofthe disclosure.

FIG. 2C shows a more detailed view of the AC three phase connectionsmade in a junction box, according to one or more illustrative aspects ofthe disclosure.

FIG. 2D shows example connections made in a junction box, according toone or more illustrative aspects of the disclosure.

FIG. 3 shows a flowchart of a method, according to one or moreillustrative aspects of the disclosure.

FIG. 4A shows a flowchart of a method, according to one or moreillustrative aspects of the disclosure.

FIG. 4B shows an implementation of step 405 as shown in FIG. 4A,according to one or more illustrative aspects of the disclosure.

FIG. 5A shows a part system block diagram and part schematic diagram ofa more detailed view of the AC three phase connections made in ajunction box, according to one or more illustrative aspects of thedisclosure.

FIG. 5B shows a junction box, according to one or more illustrativeaspects of the disclosure.

FIG. 5C shows a part system block diagram and part schematic diagram ofa more detailed view of AC three phase connections made internally in asystem power device, according to one or more illustrative aspects ofthe disclosure.

FIG. 6 illustrates a simplified block diagram of a mobile computersystem according to one or more illustrative aspects of the disclosure.

FIGS. 7A and 7B illustrate a graphical user graphical user interface(GUI) which may include various screen portions which may be provided ona display of a mobile computing system, according to one or moreillustrative aspects of the disclosure.

DETAILED DESCRIPTION

In the following description of various illustrative aspects of thedisclosure, reference is made to the accompanying drawings, which form apart hereof, and in which is shown, by way of illustration, variousaspects of the disclosure in which aspects of the disclosure may bepracticed. It is to be understood that other aspects of the disclosuremay be utilized and structural and functional modifications may be made,without departing from the scope of the present disclosure.

Reference is now made to FIG. 1A, which illustrates a block diagram of apower system 10 a, according to illustrative aspects of the disclosure.Power system 10 a includes multiple wiring configurations 111. Eachwiring configuration 111 may include one or more power sources (notshown) which may be connected to a respective power device (also notshown). Power sources may be AC power sources (e.g., wind turbines,photovoltaic panels coupled to microinverters or having integratedmicroinverters, etc.) or sources of DC power derived from wind turbines,battery banks, photovoltaic solar panels, rectified alternating current(AC) or petrol generators for example. Each wiring configuration 111 mayinclude output terminals A and B. The outputs on terminals A and B ofthe wiring configurations 111 may be connected in series to form aseries connection of wiring configuration 111 outputs. The seriesconnection of wiring configuration 111 outputs may be connected to inputterminals C and D of a link unit 107.

According to different aspects of the disclosure, one or more wiringconfiguration 111 does not include power devices. For example, in someaspects, a wiring configuration 111 of FIG. 1A or FIG. 1B includes asingle power generator, or multiple power generators connected in seriesor parallel.

One or more storage devices 106 may be connected to terminals E and F oflink unit 107. Storage devices 106 may be batteries, flywheels and/orsuper capacitors for example. Terminals E and F of link unit 107 may beconfigurable. Configurability of terminals E and F may allow storagedevices 106 to be charged from wiring configurations 111.Configurability of terminals E and F may allow system power devices 109to be discharged into load 104 via system power devices 109. One or moresystem power devices 109 may be connected together with respectiveinputs and outputs connected in parallel. The inputs of system powerdevices 109 may be connected to terminals G and H of link unit 107.Three system power devices 109R, 109M and 109L are shown with respectiveinputs and outputs connected in parallel. The outputs of system powerdevices 109 may be connected to load 104 and/or multiple loads 104.System power devices 109 according to illustrative aspects of thedisclosure may be DC to AC inverters and load 104 may be an AC utilitygrid for example. As another example, system power devices 109 may becombiner boxes, and load 104 may be a utility grid or a DC to ACinverter connected to an AC utility grid.

Reference is now made to FIG. 1B, which illustrates a block diagram of apower system 10 b, according to illustrative aspects of the disclosure.Power system 10 b may be similar to power system 10 a except withrespect to wiring configurations 111. In power system 10 b, each wiringconfiguration 111 may include output terminals A and B. The outputs onterminals A and B of the wiring configurations 111 may be connected inparallel to form a parallel connection of wiring configuration 111outputs. The parallel connection may be connected to input terminals Cand D of a link unit 107.

A feature of link units 107 according to certain aspects may be toinclude a power device such as power devices 103 (which will bedescribed in FIG. 1C) which may convert power bi-directionally. A firstdirection of power conversion by a power device may be when multiplestorage devices 106 are sourced with converted power from the powerdevices. Storage devices 106 may receive converted power from the powerdevices when storage devices 106 are being charged. A second directionof power conversion may be when power from storage devices 106 isconverted by the power device to be supplied to loads 104 via systempower devices 109. Three system power devices 109R, 109M and 109L may beshown with respective inputs and outputs connected in parallel.

With respect to system power devices 109 which may be DC to ACinverters, a first direction of power conversion by the inverters may befrom AC to DC. The first direction may be for when multiple storagedevices 106 are sourced with converted power from load 104 which may bean AC utility grid, for example. A second direction of power conversionmay be used when power from storage devices 106 is converted byinverters to be supplied to loads 104 via system power devices 109. Thesecond direction of power conversion may also include power from powersources 101 with respective power device 103.

Reference is now made to FIG. 1C, which illustrates more details ofwiring configurations 111 shown in FIGS. 1A and 1B, according toillustrative aspects of the disclosure. Multiple strings STn may beshown in a wiring configuration 111 which are connected in parallel atterminals A and B. The output of wiring configuration 111 at terminals Aand B may connect to the input of link unit device 107 at terminals Cand D. Each wiring configuration 111 may include one or more powersources 101 which may be connected to a respective power device 103 atterminals W and X. The outputs of power devices 103 at terminals Y and Zmay be connected together to form a string STn which connects acrossterminals A and B. The connections in string STn and optionallyadditional strings STn connected to terminals A and B are provided bypower lines 120. Alternatively, strings STn may connect in series ratherthan in parallel as shown and the series connection of strings STn mayconnect across terminals A and B. According to features described aboveboth wiring configurations 111 and power sources 101/power devices 103contained in a wiring configuration 111 may be connected variousseries/parallel or parallel series combinations. Power sources 101 maycontain different types of power derived from both renewable energysources such as from sunlight, wind or wave power. Power sources 101 mayinclude non-renewable energy sources such as fuel used to drive turbinesor generators, for example.

Reference is now made to FIG. 1D, which illustrates circuitry which maybe found in a power device such as power device 103, according toillustrative aspects of the disclosure. Input and output terminals W, X,Y and Z may provide connection to power lines 120 of FIG. 1C. In somecases, power device 103 may include power circuit 135. Power circuit 135may include a direct current-direct current (DC/DC) converter such as aBuck, Boost, Buck/Boost, Buck+Boost, Cuk, Flyback and/or forwardconverter, or a charge pump. In some cases, power circuit 135 mayinclude a direct current-alternating current (DC/AC) converter (alsoknown as an inverter), such as a micro-inverter. Power circuit 135 mayhave two input terminals and two output terminals, which, according tosome aspects of the disclosure, may be the same as the input terminalsand output terminals of power device 103. According to illustrativeaspects, power device 103 may include Maximum Power Point Tracking(MPPT) circuit 138, configured to extract increased power from a powersource.

According to some aspects, power circuit 135 includes MPPT functionality(e.g., power circuit 135 may be operated to draw maximum or increasedpower from a power source connected to power circuit 135), and aseparate MPPT circuit 138 is not used. According to some features, MPPTcircuit 138 (or power circuit 135) may implement impedance matchingalgorithms to extract increased power from a power source. Power device103 may further include a controller 105 such as an analog controlcircuit, a microprocessor, Digital Signal Processor (DSP),Application-Specific Integrated Circuit (ASIC) and/or a FieldProgrammable Gate Array (FPGA).

Still referring to FIG. 1D, controller 105 may control and/orcommunicate with other elements of power device 103 over common bus 190.According to some features, power device 103 may include circuitryand/or sensors/sensor interfaces 125 configured to measure parameters.Sensors/sensor interfaces 125 may measure directly or receive measuredparameters from other connected sensors and/or sensor interfaces 125.The sensors and/or sensor interfaces 125 may be configured to measureparameters on or near power source 101, such as the voltage and/orcurrent output by power source 101 and/or the power output by powersource 101. According to some features, power source 101 may be aphotovoltaic (PV) generator which includes PV cells. Power sources 101may also include a sensor or sensor interface which may directly measureor receive measurements of the irradiance received by the PV cells. Thesensor or sensor interface may also directly measure or receive thetemperature on or near the PV generator.

Still referring to FIG. 1D, according to some features, power device 103may include communication interface 129, configured to transmit and/orreceive data and/or commands from other devices. Communication interface129 may communicate using Power Line Communication (PLC) technology,acoustic communications technology, or additional technologies such asZIGBEE™, Wi-Fi, BLUETOOTH™, near field communication (NFC), cellularcommunication or other wireless methods. Power Line Communication (PLC)may be performed over power lines 120 between power devices 103 and linkunit (e.g. DC-DC converter and/or inverter) 107 which may include asimilar communication interface to communication interface 129.

According to some features, power device 103 may include memory device123, for logging measurements taken by sensor(s)/sensor interfaces 125,for storing code, operational protocols or other operating information.Memory device 123 may be flash, Electrically Erasable ProgrammableRead-Only Memory (EEPROM), Random Access Memory (RAM), Solid StateDevices (SSD) or other types of appropriate memory devices.

Still referring to FIG. 1D, according to some features, power device 103may include safety devices 170 (e.g. fuses, circuit breakers andResidual Current Devices (RCD)). Safety devices 170 may be passive oractive. For example, safety devices 170 may include one or more passivefuses disposed within power device 103. The element of the fuse may bedesigned to melt and disintegrate when excess current above the ratingof the fuse flows through it. The fuse melting and disintegrating maytherefore disconnect part of power device 103, from power lines 120and/or power sources 101 for example, so as to avoid damage to powerdevice 103. In some cases, safety devices 170 may include activedisconnect switches, configured to receive commands from a controller(e.g. controller 105, or an external controller). The commands receivedmay short-circuit and/or disconnect portions of power device 103. Thecommands received may enable short-circuit and/or disconnect portions ofpower device 103 in response to a measurement measured by a sensor. Themeasurement may be obtained by sensors/sensor interfaces 125.

In some cases, power device 103 may include auxiliary power circuit 172.Auxiliary power circuit 172 may be configured so as to receive powerfrom a power source connected to power device 103. Auxiliary powercircuit 172 may be configured so as to provide output power suitable foroperating other circuitry components (e.g. controller 105, communicationinterface 129, etc.). Communication, electrical connecting and/ordata-sharing between the various components of power device 103 may becarried out over common bus 190. In some cases, auxiliary power circuit172 may be connected to an output of a power device 103 and designed toreceive power from power sources connected to other power devices.

Power device 103 may include or be operatively attached to a maximumpower point tracking (MPPT) circuit (e.g. a separate MPPT circuit 138 orimplemented as part of power circuit 135). The MPPT circuit may also beoperatively connected to controller 105 or another controller 105included in power device 103 which may be designated as a primarycontroller. According to some aspects of the disclosure, a primarycontroller in power device 103 may communicatively control one or moreother power devices 103 which may include controllers known as secondarycontrollers. Once a primary/secondary relationship may be established, adirection of control may be from the primary controller to the secondarycontrollers. The MPPT circuit under control of a primary and/or centralcontroller 105 may be utilized to increase power extraction from powersources 101 and/or to control voltage. Control of a primary and/orcentral controller 105 may be utilized to increase current supplied tolink unit (e.g. DC-DC converter and/or an inverter or a load) 107.According to some features, no single power device 103 may be designatedas a primary controller, and each power device 103 operates (orsub-groups of power devices operate) independently. Therefore, eachpower device 103 may operate without being controlled by a primarycontroller, or a primary controller may be separate from power devices103.

Referring still to FIG. 1D, according to some features, power device 103may include bypass unit Q9 coupled between the inputs of power circuit135 and/or between the outputs of power circuit 135. Bypass unit Q9and/or power circuit 135 may be a junction box to terminate power lines120 or to provide a safety feature such as fuses or residual currentdevices. Bypass unit Q9 may also be an isolation switch. Bypass unit Q9may be a passive device, for example, a diode. Bypass unit Q9 may becontrolled by controller 105. If an unsafe condition is detected,controller 105 may set bypass unit Q9 to ON, thereby short-circuitingthe input and/or output of power circuit 135. In one example, where thepair of power sources 101 may be photovoltaic (PV) generators, each PVgenerator may provide an open-circuit voltage at its output terminals.In this example, when bypass unit Q9 is ON, the PV generators may beshort-circuited, to provide a voltage of about zero to power circuit135. In both scenarios, a safe voltage may be maintained, and the twoscenarios may be staggered to alternate between open-circuiting andshort-circuiting PV generators. This mode of operation may allowcontinuous power supply to system control devices, as well as providebackup mechanisms for maintaining a safe voltage (e.g., operation ofbypass unit Q9 may allow continued safe operating conditions).

According to some features, the power device 103 may comprise a partialgroup of the elements illustrated in FIG. 1D. For example, a powerdevice 103 might not include power circuit 135 (e.g., power circuit 135may be replaced by a short circuit, and a single bypass unit Q9 may befeatured). In a scenario where power circuit 135 may be not present,power device 103 may be still used to provide safety, monitoring and/orbypass features.

Reference is now made to FIG. 1E, which shows a buck+boost circuitimplementation for power circuit 135, according to one or moreillustrative aspects of the disclosure. The buck+boost circuitimplementation for power circuit 135 utilizes metal oxide semi-conductorfield effect transistors (MOSFETs) for switches S1, S2, S3 and S4. Thesources of switches S1, S2, S3 and S4 may be referred to as firstterminals. The drains of S1, S2, S3 and S4 may be referred to as secondterminals. The gates of S1, S2, S3 and S4 may be referred to as thirdterminals. Capacitor C1 may be connected in parallel across therespective positive (+) and negative (−) input terminals of thebuck+boost circuit where the voltage may be indicated as V_(IN).Capacitor C2 may be connected in parallel across the respective positive(+) and negative (−) output terminals of the buck+boost circuit wherethe voltage may be indicated as V_(OUT). First terminals of switches S3and S2 may connect to the common negative (−) output and input terminalsof the buck+boost circuit. A second terminal of switch S1 may connect tothe positive (+) input terminal and a first terminal of switch S1 mayconnect to a second terminal of switch S3. A second terminal of switchS4 may connect to the positive (+) output terminal and a first terminalof switch S4 may connect to the second terminals of switch S2. InductorL1 may connect respectively between the second terminals of switches S3and S4. Third terminals of switches S1, S2, S3 and S4 may be operativelyconnected to controller 105.

Switches S1, S2, S3 and S4 may be implemented using semi-conductordevices, for example, metal oxide semiconductor field effect transistors(MOSFETs), insulated gate bipolar transistors (IGBTs), bipolar junctiontransistors (BJTs), Darlington transistor, diode, silicon-controlledrectifier (SCR), Diac, Triac or other types of semi-conductor switches.Using by way of example, switches S1, S2, S3 and S4 may be implementedby use of bipolar junction transistors. The collectors, emitters andbases of the bipolar transistors may refer to first terminals, secondterminals and third terminals described and defined above. Switches S1,S2, S3 and S4 may be implemented using mechanical switch contacts, suchas hand operated switches or electro-mechanically operated switches suchas relays. Similarly, power device 103 may include, for example, a buckcircuit, a boost circuit, a buck/boost circuit, a Flyback circuit, aForward circuit, a charge pump, a Cuk converter or any other circuitwhich may be utilized to convert power on the input of power device 103to the output of power device 103.

Reference is now made to FIG. 1F, which shows a plan view of a physicallayout for three system power devices 109R, 109M and 109L, according toone or more illustrative aspects of the disclosure. Cables forconnection of DC and AC between power devices 109R, 109M, 109L andjunction box 150 are not shown. Power devices 109R, 109M and 109L may bemounted to a wall or a frame (both not shown). The mounting may be suchthat power device 109L is mounted laterally to the left (L) of middle(M) power device 109M and power device 109R is mounted laterally to theright (R) of middle (M) power device 109M. Junction box 150 may be shownattached underneath power device 109M but also may be attachedunderneath power devices 109R and/or 109L or laterally to the sides ofeither power devices 109R, 109M or 109L. Alternatively, or in addition,an arrangement of power devices 109 may be such that power device 109Lis mounted longitudinally above middle power device 109M and powerdevice 109R is mounted longitudinally below middle power device 109M. Assuch junction box 150 may be mounted laterally to the left or right ofmiddle power device 109M or to the left or right of power device 109Rand/or power device 109L.

Middle (M) power device 109M as with power devices 109L and 109R mayinclude a data connection 14, gland 12 for an AC output cable (notshown) and gland 16 for a DC input from cables (not shown) from linkunits 107. A cable gland like glands 12, 16 and 19 in descriptions whichfollow may refer to devices designed to attach and secure the end of anelectrical cable to the housings of power devices 109R, 109M and 109Land junction box 150. Middle (M) power device 109M and/or power devices109L and 109R may also include a display 152 which is shown mounted onthe housing of middle (M) power device 109M. Attached to middle (M)power device 109M and/or the wall or the frame is a junction box 150.The attachment of middle (M) power device 109M to junction box 150 mayalso include conduits 18 a and 18 b which may provide a mechanicalattachment between power device 109M and junction box 150. Themechanical attachment may provide a tube for protecting electricalwiring conductors between device 109M and optional junction box 150.Junction box 150 may also include an isolation switch 154 and glands12L, 12M, 12R and AC output via gland 19. The isolation switch 154 maybe utilized to isolate DC from being applied to the inputs of powerdevices 109R, 109M and 109L.

By way of example, an installer may attach and secure a DC cable fromlink units 107 to the housing of power devices 109 via glands 16. Theconductors of the DC cable may pass through gland 16 to be terminatedinside the power device 109. Specifically, according to one or moreillustrative aspects of the disclosure, the DC cable from link units 107may be attached and secured to the housing of power device 109M viagland 16 of power device 109M. The conductors of the DC cable may thenbe fed through conduits 18 a and/or 18 b and terminated into atermination inside junction box 150. From the termination via theisolation switch 154, DC inputs to power devices 109L and 109R may beprovided by DC cables secured and attached between glands of junctionbox 150 and glands 16 of power devices 109L and 109R. The conductors ofthe DC cable may be terminated in power devices 109L and 109R and theother ends of the conductors terminated in junction box 150 at thetermination inside. DC input into power device 109M may be viaconductors from the termination via the isolation switch 154 throughconduits 18 a and/or 18 b and terminated in power device 109M. Theterminations of DC cables and conductors described above may also bemade in additional junction/connection boxes.

In a similar manner, if power devices 109R, 109M and 109L are threephase DC to AC inverters, a three phase AC cable may be attached andsecured at both ends of the three phase AC cable. The three phase ACcable may be attached and secured at both ends for example between gland12 of power device 109L and gland 12L of junction box 150. Theconductors of the three phase AC cable may be terminated inside therespective housings of power device 109L and junction box 150.Similarly, a three phase AC cable may be attached and secured at bothends of the three phase AC cable. Both ends of the three phase AC cablemay be between gland 12 of power device 109R and gland 12R of junctionbox 150. The conductors of the three phase AC cable may be terminatedinside the respective housings of power device 109R and junction box150. Similarly, a three phase AC cable may be attached and secured atboth ends of the three phase AC cable for example between gland 12 ofpower device 109M and gland 12M of junction box 150. Alternatively, thethree-phase connection between power device 109M and junction box 150may have conductors pass through conduits 18 a and/or 18 b. Theconductors provide the connection between power device 109 and junctionbox 150. An AC cable with conductors terminated in junction box 150 maybe attached and secured to the housing of junction box 150 by gland 19.The AC cable may provide the AC combined power output of power devices109R, 109M and 109L which may be connected to load 104.

Reference is now made to FIG. 1G, which shows a part system blockdiagram and part schematic diagram for power device 109, according toone or more illustrative aspects of the disclosure. Power device 109 maybe used to implement power devices 109R, 109M and 109L. As such, powerdevices 109R and 109L may or may not include display 152 as shown inFIG. 1F for example and/or other components of power device 109. Powerdevice 109M may include all the components of power device 109. Powerdevices 109L and 109R may include power switching circuitries 160,sensors and/or sensor interfaces 164. Power device 109M provides theother features of power device 109 to power devices 109L and 109R.Alternatively, all the features of power device 109 may be used toimplement power devices 109R, 109M and 109L. Controller 162 of powerdevice 109M may serve as a master controller to the other controllers162 of power devices 109L and 109R. Similarly, the components andfunctionality of junction box 150 may be integrated into system powerdevice 109. In some locales, safety features included in junction box150 are not required, and junction box 150 provides power combiningcircuitry (e.g. by providing connections to AC power outputs of systempower devices 109L-109R) without safety devices).

Power device 109 may include a controller 162 which provides an outputto control the operation of power switching circuitry 160. Powerswitching circuitry 160 as a DC to AC inverter may have a DC inputapplied at terminals DC+ and DC− and a 3-phase output on terminals L1,L2 and L3. Terminals L1, L2 and L3 may include Neutral (N) and earth (E)terminals. Inverter topologies for the DC to AC inverter may includehalf and full bridge inverters, a diode clamped multilevel inverter,flying capacitors multilevel inverters and/or a cascaded H-bridgemultilevel inverters. Sensor interface 164 may be operatively attachedto power switching circuitry 160 and to controller 162. Sensor interface164 may include sensors 164 a and 164 b and other sensors. Sensors 164 aand 164 b and the other sensors of sensor interface 164 may provide asense of electrical parameters such as DC voltage and/or current inputon the DC at terminals DC+ and DC. The sense of electrical parametersmay include the AC the three phase voltages of the three-phase output onterminals L1, L2 and L3. The sense of electrical parameters may furtherinclude phase differences between three phase voltages on terminals L1,L2 and L3, frequencies of three phase voltages on terminals L1, L2 andL3, total harmonic distortion (THD) on three phase voltages on terminalsL1, L2 and L3, power factors of three phase voltages on terminals L1, L2and L3, temperature of heatsinks and/or switching devices utilized inpower switching circuitry 160.

Controller 162 may connect bi-directionally to Maximum Power PointTracking (MPPT) circuit 169. MPPT circuit 169 may be configured toextract increased power from the output of link unit 107 at terminals Gand H with respect to FIGS. 1A and 1B for example. MPPT circuit 169 mayimplement impedance matching algorithms to extract increased power froma power source. Controller 162 may further include amicroprocessor/microcontroller, Digital Signal Processor (DSP),Application-Specific Integrated Circuit (ASIC) and/or a FieldProgrammable Gate Array (FPGA). In some aspects, MPPT circuit 169 may beimplemented as part of power switching circuitry 160, or might not beimplemented at all (e.g. if MPPT functionality is not needed or desired,for example, if MPPT is applied by a power device connected between the(e.g., DC) input to system power device 109 and a power source.

Controller 162 and the other components of power device 109 may alsoreceive an operating power from auxiliary power circuit 163. The othercomponents of power device 109 may include communication interface 166and MPPT circuit 169, etc. Controller 162 and the other components ofpower device 109 may be configured to receive power from a power sourceconnected to link unit 107. In some embodiments, auxiliary power circuit163 may be designed to receive power from power sources connected toother power devices and power converters, and/or auxiliary power circuit163 may be designed to receive power from an electric grid.

Controller 162 may include a microprocessor or microcontroller which maybe connected bi-directionally to memory 168 and communications interface166. Communications interface 166 may communicate between power devices109M, 109L and 109R using power line communication (PLC) technology,acoustic communications technology, or additional technologies such asZIGBEE™, Wi-Fi, BLUETOOTH™, near field communication (NFC), cellularcommunication or other wireless methods. Power Line Communication (PLC)may be performed over power lines between power devices 103/powerdevices 109M, 109L and 109R and link units 107. Communication interface166 may be a similar communication interface to communication interface129 as described above. Communication interface 166 may providecommunications between power devices 109M, 109L and 109R described belowin further detail. Communication interface 166 may provide a connectionto a local network and/or a cellular network. The connection may be alsoto an internet connection to and/or between power devices 103/powerdevices 109M, 109L and 109R and link units 107. The components of powersystems 10 a and 10 b may include power devices 103/power devices 109M,109L and 109R and link units 107 for example. The connectability to thelocal network and/or a cellular network may be remote and/or via amobile computing device. The mobile computing device may be in theproximity of the components of power systems 10 a and 10 b which mayallow an access to the components. The access may include, for example,updates of firmware to the components, remote and/or local monitoring ofeach component in power systems 10 a and 10 b for example. The accessmay additionally include real time re-configuration of the componentsresponsive to monitored parameters sensed by sensors 125 andsensors/sensor interface 164 of power device 109. The access may help toestablish the identity and topographical location of a componentrelative to other components according to detailed descriptions whichfollow.

Reference is now made to FIG. 2A, which shows a more detailed view ofthe inside contents of a junction box 250. The inside contents mayinclude components which connect via cables and/or conduits to powerdevices 109L, 109M, 109R, according to one or more illustrative aspectsof the disclosure. Deutsches Institut für Normung (DIN) rail 208 may bemounted to the back panel of junction box 250. DIN rail 208 may befurther utilized to mount DC circuit breakers 206, isolation switch 254and AC circuit breakers 204. Another DIN rail 208 is shown which showstwo terminal blocks 264 which may be utilized to terminate both AC andDC conductors. Further mounted to the back panel of junction box 250 maybe ground terminal 200 which may connect electrically to DIN rail 208.According to some aspects, ground terminal 200 may connect to the earth(E) of AC circuit breaker 204, and according to some aspects, groundterminal 200 may connect to a separate earth terminal, or might not beconnected to any earth terminal (e.g., where the DC power input tojunction box 250 is “floating” with respect to the AC output of junctionbox 250). As such, the housings of junction box 250 and/or power devices109R, 109M and 109L may conform to the standard of a Class II or doubleinsulated housing. An example of the Class II or double insulatedhousing may be according to International Standard IEC 61140 or StandardBSI BS 2754; Memorandum: “Construction of Electrical Equipment forProtection Against Electric Shock”). With respect to junction box 250,compliance of the housings to Class II may provide for the option of nothaving an electrical connection between ground terminal 200 andelectrical earth (E). Similar safety consideration with respect Class IImay also apply to the housings of other component parts included inpower systems 10 a and 10 b such as link units 107, storage devices 106and wiring configurations 111 for example.

Additional terminal blocks 264 may also be mounted on DIN rail 208and/or the back panel/sides of junction box 250. The additional terminalblocks 264 may be added in order to expand the terminals provided by DCcircuit breakers 206, isolation switch 254 and AC circuit breakers 204.Wire 265 connects terminal blocks 264 to AC circuit breakers 204. DCconductors DC+ and DC− from a cable attached and secured to a link unit107 for example are shown coming through a conduit and terminated in theinput of isolation switch 254. The other end of the cable may be securedand attached to power device 109M by gland 16 of power device 109M. Theoutput of isolation switches 254 may be terminated on the DC+ and DC−input of DC circuit breakers 206.

The AC three phase power output of power device 109M may be viaconductors live L1, live L2, live L3, neutral N and Earth (E) throughconduit 18 b and may be terminated in corresponding terminals of ACcircuit breaker 204. Alternatively, The AC three phase power output ofpower device 109M may be connected by an AC three phase cable betweengland 12 of power device 109M and gland 12M of junction box 250. Theconductors of the AC three phase cable may be terminated respectively interminals L1, L2, L3, neutral (N) and Earth (E) terminals of powerdevice 109M and in corresponding input terminals of AC circuit breaker204. The AC three phase power output of power device 109L may beconnected by an AC three phase cable between gland 12 of power device109L and gland 12L of junction box 250. Similarly, The AC three phasepower output of power device 109R may be connected by an AC three phasecable between gland 12 of power device 109R and gland 12R of junctionbox 250. The output of AC circuit breaker 204 may therefore provide theAC combined power outputs of power devices 109R, 109M and 109L. Theoutput of AC circuit breaker 204 may be connected to load 104 via athree-phase cable secured and attached to the housing of junction box250 by gland 19.

One advantage of AC combined power outputs of power devices 109R, 109Mand 109L and the mounting of 109R, 109M and 109L onto a frame and/or awall may be to aid in the installation by a single operative. Incontrast, a single power device 109, which provides the same combined ACpower output as power devices 109R, 109M and 109L, may be bulker and/orheavier. Thus the single power device may require multiple operativesand/or additional lifting equipment to mount the single power device 109on onto a frame and/or a wall. Another benefit of having modularinverters provides flexibility in increasing or reducing the size of aphotovoltaic PV installation by simplifying and reducing the work inadding or removing inverters. As yet another advantage, having multiplemodular inverters provides an increased level of reliability. Manyphotovoltaic PV installations may be operated at less thanpeak-production capacity for significant periods of time. In case asingle system power device (e.g., inverter) malfunctions, the other twosystem power devices may continue to operate. The other two system powerdevices may provide at least two-thirds (and potentially more, dependingon current system generation capacity) of the power otherwise providedby the three system power devices.

Reference is now made to FIG. 2B, which shows a more detailed view ofthe AC three phase connections made in junction box 250, according toone or more illustrative aspects of the disclosure. Power device 109Lmay be mounted/positioned laterally to the left (L) of middle (M) powerdevice 109M and power device 109R may be mounted/positioned laterally tothe right (R) of middle (M) power device 109M. Each power device 109R,109M and 109L has a three-phase output on terminals L1, L2 and L3.Connections between the three-phase output on terminals L1, L2 and L3 ofeach power device 109R, 109M and 109L and junction box 250 may be by ACthree-phase cables as described above with respect to the descriptionsof FIG. 1F.

As mentioned previously (with respect to FIG. 2A), additional terminalblocks 264 may also be mounted on DIN rail 208 and/or the backpanel/sides of junction box 250. The additional terminal blocks 264 maybe added in order to expand the terminals provided by DC circuitbreakers 206, isolation switch 254 and/or AC circuit breakers 204. Inthe case where terminal blocks 264 are provided to connect AC outputterminals of multiple inverters (e.g. system power devices 109L-109R),the additional terminal block may enable the swapping of the phases ofthe conductors terminated in additional terminal blocks 264. As such,the conductors of the AC three phase cables may be terminated at one endin respective terminals L1, L2 and L3 of each power device 109R, 109Mand 109L. The other ends of the AC three phase cables conductors may beterminated in terminals labelled as L1, L2 and L3 provided in junctionbox 250.

The three-phase output 25 (conductors L1, L2, L3, and not shown N) fromthe other side of AC circuit breakers 204 of junction box 250 may beprovided via an AC three phase cable. The AC three phase cable may beattached and secured to the housing of junction box 250 by gland 19.

The AC three phase cables conductors may be terminated in terminals L1,L2 and L3 of AC circuit breakers 204. By virtue of the additionalterminal blocks 264 it may be such that L1 conductors of power devices109R, 109M and 109L connect to the L1 terminal of AC circuit breakers204; L2 conductors of power devices 109L and 109M connect to the L2terminal of AC circuit breakers 204 but L3 conductor of power device109R connects to the L2 terminal of AC circuit breakers 204; L3conductors of power devices 109L and 109M connect to the L3 terminal ofAC circuit breakers 204 but L2 conductor of power device 109R connectsto the L3 terminal of AC circuit breakers 204.

Reference is now made to FIG. 2C, which shows a more detailed view ofthe AC three phase connections made in junction box 250, according toone or more illustrative aspects of the disclosure. FIG. 2C shows thesame connections with respect to AC circuit breakers 204 described abovebut further includes proximity sensors 17 a and respective targets 17 b.

Proximity sensors 17 a may be configurable to detect the presence ofnearby power device 109. For example, two proximity sensors 17 a ofpower device 109M may be utilized to provide a detection of powerdevices 109L and 109R. The detection may be by virtue of proximitysensor to provide a transceiver function. The transceiver function maybe such that a reflected signal form target 17 a for a signal sent byproximity sensor 17 a may be received by proximity sensor 17 a. Targets17 b may be passive or active RFID tags for example or may include alongwith proximity sensor 17 a a near field communication (NFC). The NFC maybe a short-range wireless connectivity standard that uses magnetic fieldinduction to enable communication between power devices 109 when theyare touched together, or brought within a few centimeters of each other.Other alternatives for proximity sensors 17 a and targets 17 b mayinclude capacitive proximity sensor types such as capacitivedisplacement sensors, doppler effect (sensor based on effect),eddy-current, inductive, magnetic, including magnetic proximity fuse.Optical sensors may include optical photocells (reflective), laserrangefinder, passive (such as charge-coupled devices) passive thermalinfrared. Other types of sensor may further include radar, reflection ofionizing radiation, sonar (typically active or passive), ultrasonicsensor (sonar which runs in air), fiber optics sensor and/or Hall effectsensor.

Proximity sensors 17 a and targets 17 b may be located on a surface ofthe housings of power devices 109L, 109M and 109R, embedded in thesurface or inside of the housings of power devices 109L, 109M and 109R.In descriptions that follow proximity sensors 17 a and targets 17 b maybe utilized to obtain and verify the lateral positions left (L) andright (R) of respective power devices 109L and 109R relative to middle(M) power device 109M. Obtaining and verifying the lateral positions mayenable monitoring for theft or un-authorized replacement and/orrepositioning of power devices 109L, 109M or 109R.

Reference is now made to FIG. 2D, which shows a more details ofconnections which may be made in junction box 150/250, according to oneor more illustrative aspects of the disclosure. As stated above and indescriptions which follow, additional terminal blocks 264 may be addedin order to expand the terminals provided by AC circuit breakers 204.Three terminal blocks 264L, 264M and 264R are shown labelled left (L),middle (M) and right (R) which may be mounted on DIN rail 208 (notshown). Cable-L connects electrically power device 109L to terminalblock 264L, cable-M connects electrically power device 109M to terminalblock 264M and cable-R connects electrically power device 109R toterminal block 264R. Glands 12L, 12M and 12R (not shown) maymechanically and/or electrically attach cable-L, cable-M and cable-R tojunction box 150/250. Electrical attachment with respect to glands 12L,12M and 12R may be with respect to wire armour/shielding of cable-L,cable-M and cable-R. Each of cable-L, cable-M and cable-R includesconductors con1, con2 and con3 which may provide phase L1, L2 and L3respectively. Conductors con1, con2 and con3 may be labelled L1, L2 andL3 and/or have respective insulation colors red (R), yellow (Y) and blue(B). Each of cable-L, cable-M and cable-R may further include neutral(N) and earth (E) conductors (not shown).

Power device 109L may be located laterally to the left of power device109M. A parallel connection in junction box 150/250 at terminal blocks264L, 264M and 264R includes cable-L electrically and mechanicallyconnecting power device 109L to power device 109M. Similarly, powerdevice 109R may be located laterally to the right of power device 109Mand the parallel connection includes cable-R electrically andmechanically connecting power device 109R to power device 109M. Furtherincluded in the parallel connection is cable-M which connects powerdevice 109M to power devices 109R and 109L. A feature of the parallelconnection made at terminal blocks 264L, 264M and 264R is that bothelectrically and in terms of labeling, phase L1 of power device 109Lterminated in terminal block 264L is substantially the same as bothphases L1 of power devices 109M and 109R terminated in respectiveterminal blocks 264M and 264R. Similarly, phase L2 of power device 109Lterminated in terminal block 264L is substantially the same as bothphases L2 of power devices 109M and 109R terminated in respectiveterminal blocks 264M and 264R. Similarly phase L3 of power device 109Lterminated in terminal block 264L is substantially the same as bothphases L3 of power devices 109M and 109R terminated in respectiveterminal blocks 264M and 264R.

Connection between terminal blocks 264L, 264M, 264R and AC circuitbreaker 204 is by wires 256 (as shown partially in FIG. 2A). Connectionbetween terminal blocks 264L, 264M, 264R and AC circuit breaker 204 mayinclude connection of terminals L1 of terminal blocks 264L, 264M and264R connected together and to terminal L1 of AC circuit breaker 204.Therefore, terminals and label L1 and cable con1 of AC circuit breaker204 are the same as phases L1 of terminal blocks 264L, 264M and 264R.Terminals L2 of terminal blocks 264L and 264M are connected together andfurther connected to terminal L2 of AC circuit breaker 204. Connection266 in AC circuit breaker 204 provides a swap and connection of phasesL2 and L3 of terminal block 264R, therefore the three-phase output 25via gland 19, provides phases L1, L2 and L3 on respective conductorscon1, con2′ and con3′ of an AC output cable (not shown) terminated in ACbreaker 204 on terminals labeled respectively as L1, L2 and L3.Connection 266 in AC circuit breaker 204, therefore, provides the swapand connection of phases L2 and L3 of terminal block 264R. The labellingon the three-phase output 25 means that Phase L1 is the same phase,label, terminal throughout junction box 150/250. However,phases/terminals/labels of L2 and L3 on three-phase output 25 are notthe same as phases/terminals/labels of L2 and L3 of terminal block 264Rsince connection 266 in AC circuit breaker 204 provides the swap andconnection of phases L2 and L3 of terminal block 264R.

A phase swap relay 267 (shown by dotted box) may be utilized to swapphases L2 and L3. In a first switch state of phase swap relay 267,terminals/labels/phases L1, L2 and L3 are substantially the same onterminal blocks 264L, 264M, 264R and AC circuit breaker 204. However, asecond switch state of phase swap relay 267, may provide the swap ofphases L2 and L3 of terminal block 264R according to connection 266 inAC circuit breaker 204 in the description described above. Thedescription above and ones below swaps phases L2 and L3, however, swapsmay be between phases L1 and L3 or between phases L1 and L2.

Reference is now made to FIG. 3, which shows a flowchart of a method300, according to one or more illustrative aspects of the disclosure. Atstep 301, referring back to FIGS. 1F, 2B, 2C and 2D, an installer maymount power devices 109R, 109M and 109L to a wall or a frame (both notshown) such that power device 109L is mounted laterally to the left (L)of middle (M) power device 109M and power device 109R is mountedlaterally to the right (R) of middle (M) power device 109M.

At step 303, a parallel connection may be provided which may include thetermination of the AC three phase cables conductors inside power devices109R, 109M and 109L and junction box 250 by an installer. Whereas, thefeature of swapping two of the phases may already be provided injunction box 250 supplied to an installer. The parallel connection maybe by the installer using a wiring diagram so that the parallelconnection may be as described in FIGS. 2B, 2C and 2D. The parallelconnection may include a parallel connection of the DC+ and DC−connection of the inputs of power devices 109R, 109M and 109L and/or aparallel connection of the AC outputs of power devices 109R, 109M and109L.

The wiring diagram may be a simple visual representation of the physicalconnections such as cables terminations and physical layout which mayinclude the components of power devices 109R, 109M, 109L and junctionbox 250. The wiring diagram may also show how the electrical wires orconductors are interconnected inside power devices 109R, 109M, 109L asthey relate to the components of junction box 250. The components ofjunction box 250 may include DC circuit breakers 206, isolation switch254, terminal blocks 264 and AC circuit breakers 204 shown in FIG. 2Afor example. Conductors of AC cables may be labelled as L1, L2 and L3 ormay color coded such that L1, L2 and L3 correspond respectively red,yellow and blue for example.

With respect to the AC three phase cables conductors terminated interminals L1, L2 and L3 of junction box 250 as described above,interconnection features of junction box 250 at step 305 may terminatethe AC cable between power device 109R and the terminals of AC circuitbreakers 204. Termination of the AC cable may be such that conductors L2and L3 of the cable are terminated in respective terminals L3 and L2 ofAC circuit breakers 204. In other words, terminals provided by ACcircuit breakers 204 labelled as phases L2 and L3 swap respective phasesL3 and L2 of the conductors of the cable. For example, the L1 conductorof junction box 250 may be connected to the L1 terminal of each ofsystem power devices 109L-109R. The L2 conductor of junction box 250 maybe connected to the L2 terminal of system power devices 109L and 109M,but to the L3 terminal of system power device 109R. The L3 conductor ofjunction box 250 may be connected to the L3 terminal of system powerdevices 109L and 109M, but to the L2 terminal of system power device109R. Arranging the phase connections in this manner may provide certainbenefits, as will be described below.

Reference is now made to FIG. 4A, which shows a flowchart of a method400, according to one or more illustrative aspects of the disclosure.Method 400 describes the operation of a parallel connection of powerdevices 109L, 109M and 109R where the respective DC inputs of powerdevices 109L, 109M and 109R are connected together and the respectivethree phase AC outputs of power devices 109L, 109M and 109R areconnected together. Method 400 may be carried out by multiplecontrollers. The combined DC input to power devices 109L, 109M and 109Rfrom link units 107 may be terminated at terminals DC+ and DC− of DCcircuit breakers 206 for example. The combined DC input may pass throughDC circuit breakers 206 and isolation switch 254 and into the parallelconnected DC input of power devices 109L, 109M and 109R. At step 401,using by way of example a total DC input power of 99 Kilo Watt (KW) intothe parallel connected DC input to power devices 109L, 109M and 109R.

In some cases, the DC inputs of power devices 109L, 109M and 109R arenot connected together. According to different aspects of the disclosureherein, each of power devices 109L-109R might be connected to a separateDC power source (e.g. a photovoltaic generator or a battery) with the ACoutputs of power devices 109L-109R combined in parallel.

As a numerical example, each power device 109L, 109M and 109R mayconvert 33 KW of DC power input to a 33 KW three phase AC output fromeach power device 109L, 109M and 109R. A combined three phase AC outputof substantially 99 KW provided on terminals L1, L2 and L3 of AC circuitbreakers 204 may be provided by virtue of the parallel connection of therespective three phase AC outputs of power devices 109L, 109M and 109R.

A parameter such as phase difference between phases L1, L2 and L3 may besensed at the by sensor 164 b/sensor interface 164 of power device 109Mat step 403. By virtue of phases L2 and L3 being previously swapped injunction box 250 at step 305, of method 300, different parameters may bemeasured at the power devices. The results of sensing step 403 may beshown in Table 1 below:

TABLE 1 Power L1-L2 Phase L1-L3 Phase Sign converter differencedifference (L1-L2) 109L 120 −120 1 109M 120 −120 1 109R −120 120 −1

Or by Table 2 below:

TABLE 2 Power L1-L2 Phase L1-L3 Phase Sign converter differencedifference (L1-L2) 109L −120 120 −1 109M −120 120 −1 109R 120 −120 1

From the above two tables, it can be seen that the right (R) powerdevice 109R always has an opposite Sign (L1-L2) with respect to theother two power devices 109M and 109L. As such, in step 405, the lateralpositions left (L) and right (R) of respective power devices 109L and109R relative to middle (M) power device 109M can be obtained. Thelateral position obtained for example may be by remote monitoringtechniques where communications interfaces 166 may be connectable to alocal network and/or a cellular network. The connection to a localnetwork and/or a cellular network may be in order to establish aninternet connection to and/or between power devices 103/power devices109M, 109L and 109R and link units 107 for example.

At step 404, a sensed parameter (e.g. phase difference) sensed by eachsystem power device 109 may be transmitted to a central controller. Thesensed parameter may also be the phase sequence of the phases. The phasesequence may be defined as the order in which the three phase voltages(L1, L2 and L3 or respectively red (R), yellow (Y) and blue (B)) attaintheir positive peak values. The phase sequence is said to be RYB if Rphase attains its peak or maximum value first followed by Y phase 120°later and B phase 240° later than the R phase. The phase sequence issaid to be RBY if R phase is followed by B phase 120° later and Y phase240° (or −120°) later than the R phase. By convention RYB may beconsidered as positive while the sequence RBY may be considered asnegative.

Based on the sensed parameters, at step 405, the central controller mayestablish the positions of the power devices. According to some aspectsof the disclosure, each system power device may, based on themeasurements, establish its (i.e., the instant system power device's)position and transmit the established position to the centralcontroller. Step 405 may additionally consider the serial number ofpower device 109M in order to verify the lateral positions left (L) andright (R) of respective power devices 109L and 109R relative to middle(M) power device 109M. Alternatively, the phase differences inconjunction as summarized in Tables 1 and 2 above and/or with the use ofproximity sensors 17 a and respective targets 17 b may be used to obtainand verify the lateral positions left (L) and right (R) of respectivepower devices 109L and 109R relative to middle (M) power device 109M.

The arrangement of FIG. 2C and the resultant Tables 1-2 areillustrative. According to features herein, phases L2 and L3 may beswapped with respect to power device 109L or 109M, or instead ofswapping phases L2 and L3, phases L1 and L2 may be swapped.

Reference is now made to FIG. 4B, which shows an implementation of step405 of method 400, according to illustrative features. At step 406,given identifying information of the system power devices (e.g. serialnumbers, ID tags etc.), the identifying information of the middle systempower device 109M may be determined, for example, by being uniquecompared to the other two system power device identifying information.For example, by virtue of being connected or connectable to a junctionbox 250, a system power device 109M may have a serial number similar toMPCxxxxx (where each ‘x’ is replaced by a number) and system powerdevices 109L and 109R may have serial numbers similar to SPCxxxxx.System power devices 109L and 109R may be generic, e.g., duringmanufacturing a position (right or left) with regard to a middle systempower device which might not be predetermined.

At step 408, the device carrying out step 405 (e.g., the centralcontroller) may compare the phase difference between phases L2 and L3 ofthe first power device to the phase difference between phases L2 and L3of the middle power device as determined at step 406. Each power deviceof the middle, first and second power devices may calculate the L2-L3phase difference by comparing the time elapsed between reaching the peakof the sine wave generated at phase L2 and reaching the peak of the sinewave generated at phase L3. For example, in a system where power devicesgenerate 3-phase 50 Hz sine waves if a power device determines thatabout 6.67 milliseconds elapse between phase L2 reaching a peak andphase L3 reaching a peak, the power device may determine that a120-degree phase shift

$\frac{1}{50\mspace{14mu} {{Hz} \cdot 3}} \approx {6.67\lbrack{msec}\rbrack}$

exists between phases L2 and L3. If a power device determines that about13.33 milliseconds elapse between phase L2 reaching a peak and phase L3reaching a peak, the power device may determine that a minus 120-degreephase shift

$\frac{1 \cdot 2}{50\mspace{14mu} {{Hz} \cdot 3}} \approx {13.33\lbrack{msec}\rbrack}$

exists between phases L2 and L3.

If, at step 408, the central controller determines that the L2-L3 phasedifference of the first power device is substantially the same as theL2-L3 phase difference of the middle power device (e.g., both phasedifferences are about 120 degrees, or both phase differences are about−120 degrees). The central controller may proceed to step 410 andestablish that the first power device is to the left of middle powerdevice and the second power device is to the right of the middle powerdevice. If, the central controller determines that the L2-L3 phasedifference of the first power device is substantially different from theL2-L3 phase difference of the middle power device (e.g., both one phasedifference is about 120 degrees, and one phase difference is about −120degrees). The central controller may proceed to step 412 and establishthat the first power device is to the right of middle power device andthe second power device is to the left of the middle power device.

According to some aspects of the disclosure herein, step 405 may includecomparing phase sequences measured at step 404. For example, if themiddle power device and the first power device both have a phasesequence of L1, L2, L3, while the second power device has a phasesequence of L1, L3, L2. The central controller may determine, at step408, that the first power device and the middle power device have aboutthe same L2-L3 phase difference, and proceed to step 410. If the middlepower device has a phase sequence of L1, L2, L3, while the first powerdevice has a phase sequence of L1, L3, L2, the central controller maydetermine, at step 408, that the first power device and the middle powerdevice have a substantially different L2-L3 phase difference, andproceed to step 412.

Automatic detection of relative position of system power devices 109Land 109R with respect to system power device 109M may enable rapidlocalization of a malfunction while allowing generic manufacturing andshipping of system power devices 109L and 109R. For example, systempower device 109L may be substantially identical to system power device109R, and the decision which system power device to mount on the rightand which system power device to mount on the left may be arbitrarilymade by an installer. Once a controller (e.g., a centralized systemcontroller included in or connected to a monitoring system) hasestablished the physical location of each system power device, in caseof malfunction of a system power device, the controller may provide anindication (e.g., on a Graphical User Interface or via a message) of thephysical location of the malfunctioning device. Where all three powerdevices 109 may be generic, method 400 may be able to provide anindication that one inverter is to the left or the right of the otherthe two inverters.

Reference is now made to FIG. 5A, which shows a part system blockdiagram and part schematic diagram 500 of a more detailed view of the ACthree phase connections made in junction box 250, according to one ormore illustrative aspects of the disclosure. The AC three phaseconnections made in junction box 250 may be in the additional terminalblocks 264 which may be added in order to expand the terminals providedby AC circuit breakers 204. The three-phase output 50 (conductors L1,L2, L3, N, E) from the other side of AC circuit breakers 204 of junctionbox 250 may be provided via an AC three phase cable attached and securedto the housing of junction box 250 by gland 19. The AC three phaseconnections made in junction box 250 include a common neutral (N) whichconnects together the neutral terminals of power devices 109L, 109M and109R together. The common neutral is also provided to three-phase output50. Terminal L1 may be provided in the terminals of junction box 250 asthe connection between L2 of power device 109L to L3 of power device109M and L1 of power device 109R. Terminal L2 may be provided in theterminals of junction box 250 as the connection between L3 of powerdevice 109L to L1 of power device 109M and L3 of power device 109R.Terminal L3 may be provided in the terminals of junction box 250 as theconnection between L1 of power device 109L to L2 of power device 109Mand L2 of power device 109R.

The AC three phase connections made in junction box 250 may be such thatauxiliary power circuits 163L, 163M, 163R and their respective powerdevice 109L, 109M, 109R, receive an operating power from AC outputphases L1 and neutral (N), L2 and N, L3 and N as opposed to operatingpower from one phase (L1 for example) and neutral (N). The power fromphases L1 and neutral (N), L2 and N, L3 and N to respective powercircuits 163L, 163M, and 163R allow for a harmonic distortion as well asload sharing to be shared across phases L1, L2 and L3 as opposed to onephase. Use of one phase as well as not load sharing shared across phasesL1, L2 and L3 may not satisfy an operating a code such as German LowVoltage Grid Code VDE-AR-N-4105 (LVGC) for example. LVGC VDE-AR-N-4105includes requirements related to phase balancing, frequency-based powerreduction, reactive power control, inverter reconnection conditions,total harmonic distortion, power factor and output power control. Otherinternational standards for grid converters may include, for example,IEEE 929-2000: Recommended Practice for Utility Interface ofPhotovoltaic (PV) Systems, IEC 61727; “Characteristics of the utilityinterface for photovoltaic (PV) systems”; International ElectrotechnicalCommission, IEC 61727, 2002 and EN61000-3-2-A standard for currentharmonics.

As with descriptions above with respect methods 300 and 400, methods 300and 400 may be applied to the AC three phase connections made injunction box 250 as shown in FIG. 5A. With respect to method 300 whereat step 305 circuit breakers 204 terminate the AC cable between powerdevice 109R and the terminals of AC circuit breakers 204. As such,conductors L2 and L3 of the cable may be terminated in respectiveterminals L3 and L2 of AC circuit breakers 204. In other words,terminals provided by AC circuit breakers 204 labelled as phases L2 andL3 swap phases L3 and L2 of the conductors of the cable. The swap ofphases in step 305 and subsequent operation according to the steps ofmethod 400 allows a parameter such as phase difference between phasesL1, L2 and L3 to be sensed by sensor 164 b/sensor interface 164 of powerdevice 109M at step 403 as result of the conversion of DC power to ACpower at step 401. The results of sensing step 403 may be shown in Table1 and 2 as shown above. Consequently, at step 405, the lateral positionsleft (L) and right (R) of respective power devices 109L and 109Rrelative to middle (M) power device 109M can be obtained for example byremote monitoring techniques.

The remote monitoring techniques may be where communications interfaces166 are connectable to a local network and/or a cellular network. Theconnection to a local network and/or a cellular network may be in orderto establish an internet connection to and/or between power devices103/power devices 109M, 109L and 109R and link units 107 for example.Step 405 may additionally consider the serial number of power device109M in order to verify the lateral positions left (L) and right (R) ofrespective power devices 109L and 109R relative to middle (M) powerdevice 109M. Alternatively or additionally, the phase differences assummarized in Tables 1 and 2 above and/or with the use of proximitysensors 17 a and respective targets 17 b may be used to obtain andverify the lateral positions left (L) and right (R) of respective powerdevices 109L and 109R relative to middle (M) power device 109M.

The connections illustrated in FIG. 5A may be summarized as shown inTable 3 below:

TABLE 3 Device L1 is Device L2 is Device L3 is Power connected toconnected to connected to Device output phase output phase output phase109L L3 L1 L2 109M L2 L3 L1 109R L1 L3 L2

Since each auxiliary power circuit 163 may draw power from the neutral(N) and power device L1 terminals, by connecting each L1 system powerdevice terminal to a different phase of three-phase AC output 50. Eachauxiliary power circuit 163 may also draw power between phases, forexample between phase L1 and L2 or any other combination of phases. Thetotal auxiliary power drawn by system power devices 109L-109R maytherefore be divided evenly among the phases of three-phase AC output50. Auxiliary power drawn evenly may improve the balance and harmoniccontent of three-phase AC output 50. Further, by system power devices109L and 109R having different phase sequences (e.g., system powerdevice 109L having a phase sequence of L3-L1-L2 and system power device109R having a phase sequence of L1-L3-L2). The physical location ofsystem power devices 109L and 109R with reference to system power device109M (e.g. to the left or right of system power device 109M) may bereadily determined as disclosed above.

Reference is now made to FIG. 5B, which shows a junction box 250according to illustrative features. Junction box 250 may be the same asjunction box 250 of FIG. 5A, with connector terminals 520 a-520 c, 521a-521 c, 522 a-522 c and 523 a-523 c explicitly shown. Connectorterminals 520 a-523 a may be provided for connecting to a first systempower device (e.g. 109L), connector terminals 520 b-523 b may beprovided for connecting to a second system power device (e.g. 109M), andconnector terminals 520 c-523 c may be provided for connecting to athird system power device (e.g. 109R). Each connector terminal may belabeled to indicate an intended use. For example, connector terminal 520a may be labeled ‘N’, to indicate its intended connection to a neutralterminal connector of a system power device. Connector terminal 521 amay be labeled ‘L1’, to indicate its intended connection to an L1terminal connector of a system power device, and so on.

Labeling may be done using alphanumeric symbols, for example, or usingdifferent colors. In an installation where system power devices alsoinclude labeled connector terminals, it may be simple for an installerto connect three system power devices to junction box 250 according tothe labels, with a potentially beneficial wiring scheme. The potentiallybeneficial wiring scheme may already be provided internal to junctionbox 250 to an installer. Use of the potentially beneficial wiring schememay decrease the time associated with the system installation. Two ofthe phases swapped may help determine lateral positions of powerconverters 109 relative to each other. The other connection describedabove may also ensure total auxiliary power drawn by system powerdevices 109L-109R may be divided evenly among the phases of three-phaseAC outputs 50.

Reference is now made to FIG. 5C, which illustrates a part system blockdiagram and part schematic diagram 501 of a more detailed view of ACthree phase connections made internally in a system power device. Systempower device 119M may be similar to system power device 109M, includingintegrating some or all of elements and/or functionality of junction box250 of FIGS. 5A-5B. System power device 119 may include terminals forconnecting to phases L1-L3 of system power device 109L and terminals forconnecting to phases L1-L3 of system power device 109R. The wiringarrangement combining the AC power of system power devices 109M, 119Mand 109R may be implemented similarly to the arrangement shown in FIG.2C or the arrangement shown in FIG. 5A. Three-phase output 50 may beoutput directly from system power device 119M.

Reference is now made to FIG. 6 which illustrates a simplified blockdiagram of a mobile computer system 60 according to one or moreillustrative aspects of the disclosure. Mobile computer system 60 maybe, for example, an IPHONE™ of Apple Inc., a laptop computer or asmart-phone configured to run an ANDROID™ open operating system. Mobilecomputer system 60 may be connectible over a network 624 to a server626. Mobile computer system 60 may be also connectible through acellular base station transceiver 620 to the remainder of cellularnetwork 622. Mobile computer system 60 may include a processor 600connected to local data storage 602. A data communications module 608may connect processor 600 to network 624. A cellular communicationsmodule 604 may connect processor 600 to cellular network 622, andcellular network 622 may be further connected to the internet.

Mobile computer system 60 may include one or more devices connected toprocessor 600. For example, one or more peripheral accessory devicessuch as a display 606, global positioning system (GPS) 610, camera 612,a microphone 614, a speaker 618, a vibrator 616, accelerometer/gravitysensor/gyroscopic sensor unit 628, BLUE-TOOTH™, infra-red sensor (notshown). Display 606 may provide a graphical user interface (discussedlater) to an operator for an application, which runs on mobile computingsystem 60. An operator of mobile computer system 60 may be able tooperate the graphical user interface in the proximity of power devices109 (for example power devices 109L, 109M), link units 107 and powerdevices 103 or remotely via an internet connection. The internetconnection may be via a local network and/or a cellular network forexample.

Reference is now made to FIG. 7A which illustrates a graphical userinterface (GUI) 700, which may include various screen portions of whichmay be provided on display 606 of mobile computing system 60, accordingto one or more illustrative aspects of the disclosure. In descriptionswhich follow, mobile computing system 60 and/or another computing systemmay be located in the vicinity of power systems 10 a/10 b and/orremotely via an internet connection for example.

Screen areas 70, 71 and 71 a of GUI 700 may be included on one graphicalscreen or be displayed on different graphical screens (e.g. depending onthe screen size available). In the description that follows, a touchscreen may be referenced by way of example but other screens such ascomputer monitors may be used where items may be selected, for example,by mouse and pointer.

In the descriptions which follow, screen areas 70, 71 and 71 a of GUI700 may provide upload and download of data from server 626/network 624,a remote server as well as data from one mobile computing system 60 toanother mobile computing system 60 directly. Upload and download of datamay also be by use of communication circuits such as communicationinterfaces 129 and/or data communications module 608, existingcommunication circuits and/or a combination of retrofit communicationcircuits, existing communication circuits and power line communications(PLC). The data may include, for example, sensed and measured parametersfrom sensors/sensor interfaces 125/164 such voltages, currents, power,impedance, power factor, phase angle, harmonic distortion in phasesand/or temperature. The data may also include, for example,configuration data or firmware upgrades for link units 107, storagedevices 106, power devices 103 and power devices 109 for example.

In general, screen areas each may serve overall as an icon which whentouched or swiped by the user using a touch screen device such as asmart phone, allows a number of sub menu options to appear. The sub menumay for example allow the user to view another power system or distinctseparate portions of power system.

GUI 700 may include, for example, a master screen area 70 which may givea user information as to the location of power systems 10 a/10 b forexample. The local time and date, an indication as to the weatherconditions at the location, temperature at the location and the windspeed at the location of a power system 10 a/10 b. The local time anddate may be common to each of the screen areas described below but otherinformation may be displayed also or in addition to the local time anddate for example. Two example menu buttons are displayed which may givetwo example usages of an application running on mobile computing system60 via two menu buttons: a maintenance/monitoring menu button, aninstaller's/commissioning menu button. Other buttons may be added, suchas the provision of a site management function for example. In thedescription that follows each of the screen areas may be presented to auser regardless of which of the two buttons is selected. However, eachscreen area whilst similar in appearance may present different optionsto the user depending on which of the two buttons is selected. Accessand/or levels of access may also be provided to various screen areas byuse of usernames and passwords for example.

Screen area 71 may include (e.g., in response to theinstall/commissioning button being selected by a user) a partialtopographical map and/or system block diagram. The partial topographicalmap and/or system block diagram may show inputs and outputs betweenwiring configurations 111, link units 107, storage devices 106 and powerdevices 109 of power systems 10 a/10 b for example. The other componentsof power systems 10 a/10 b may be revealed by swipe of a finger of theuser across the screen of mobile computing device 60. The partialtopographical map and/or system block diagram may be preloaded intomobile computing device 60. The preloading may be as a result of adesign specification for power systems 10 a/10 b or may be added as partof a mapping algorithm used by a user/installer as they go aboutinstalling and/or commissioning components of power systems 10 a/10 b.

Functionality of screen 71 may allow the user/installer to enter an IDnumber for a component of power systems 10 a/10 b. How each of thecomponents are connected to each other electrically as well as how thecomponents are mapped in terms of location and adjacencies to eachother. For example, screen area 71 a may be a sub screen area if awiring configuration 111 icon is pressed. The sub screen may showfurther details of wiring configuration 111 to include a string of powerdevices 103 outputs, where the input of each power device 103 isconnected to a power source 101 (photovoltaic panel for example).

Screen 71 a my further include ID numbers to be entered for eachcomponent, to display designed voltages (V) and currents (A) as well asfor example to allow a user/installer to enter the angle of aphotovoltaic (PV) panel and/or location of the PV panel/power source 101for example. Screen area 71 a may (e.g., in response to theinstall/commissioning button being selected by a user) allow faultfinding in the string by activating bypass units Q9 with respect topower devices 103. The results of the activation of bypass units Q9 maybe monitored in terms of voltages (V) and currents (A) sensed bysensors/sensor interfaces 125 in screen area 71 a. For example, a lowerthan expected string current in the string and the use of bypass unitsQ9 may help to identify a faulty power source 101 and/or power circuit135 for example. Monitoring and operation of bypass units Q9 of thestring may be when an operative is in the proximity of the components ofpower systems 10 a and 10 b with mobile computing device 60 and/or beconnected to a local network and/or a cellular network. Connection to alocal network and/or a cellular network may be in order to establish aninternet connection to and/or between power devices 103/power devices109M, 109L and 109R and link units 107 for example.

Reference is now made to FIG. 7B which illustrates a graphical userinterface (GUI) 700, which may include various screen portions ofgraphical user interface (GUI) 700, according to one or moreillustrative aspects of the disclosure. In the context of theinstall/commissioning button being selected by a user, screen area 71 bmay be a sub screen as a result of pressing the power device 109 iconshown by hashed lines in screen area 71. Pressing the power convertericon may reveal in screen area 71 b power devices 109L, 109M, 109R andjunction box 250 according to features described above with respect tothe parallel connection of power devices 109L, 109M and 109R to providea combined AC three phase output. Screen area 71 b provides a verticalslider 72 to show further details of power device 109M (partially shown)and power device 109L (not shown). Additional operating features ofjunction box 250, power device 109R and power device 109M may berevealed by respective vertical sliders 72 a, 72 b and 72 c. In thecontext of the install/commissioning button being selected by a user, inscreen area 71 b, if the icon for junction box 250 is pressed may allowan installer to view a wiring diagram for junction box 250 similar toFIG. 2A for example. The wiring diagram may show how the electricalwires or conductors to the components of junction box 250 such as DCcircuit breakers 206, isolation switch 254 and how they relate to ACcircuit breakers 204 for example. Conductors of AC cables may belabelled as L1, L2 and L3 or may color coded such that L1, L2 and L3correspond respectively red, yellow and blue for example.

With respect to the context of installation and commissioning, detailsof the operating parameters displayed may be as a result of a provisionof a configuration to power devices 109L, 109M and 109R. Theconfiguration may be when an installer with mobile computing system 60and/or another computing system is located in the vicinity of powersystems 10 a/10 b and/or remotely via an internet connection forexample. The configuration for example may include configurationparameters for power devices 109L, 109M and 109R to share the powerconversion by system power devices 109L, 109M and 109R to a loadaccording to a prescribed function. The prescribed function may alloweach system power device 109L, 109M and 109R to autonomously determineits share of power conversion. Each system power device 109L, 109M and109R may then operate according to its own power conversionformula/function, such that overall the parallel connected system powerdevices 109L, 109M and 109R share the power conversion to a load in apredetermined manner.

With respect to the context of commissioning, monitoring/sensing (step403) the operating parameters for power device 109R with sensors 164a/164 b for example may include a sign value: Sign=1 as shown anddescribed above with respect to Table 2. Sign=1 may indicate that powerdevice 109R is positioned laterally to the right (R) of power device109M. Where with respect to power device 109L sign value: Sign=−1indicates that power device 109L is positioned laterally to the left (L)of power device 109M. Commissioning, monitoring/sensing (step 403) modemay help a user to identify and/or confirm that power device 109R ispositioned laterally to the right (R) of power device 109M.Commissioning, monitoring/sensing (step 403) may be by a user inproximity to power devices 109L, 109M and 109R or remotely connected byan internet connection. As such, according to method 400 described aboveand utilized in screen area 71 b, a user may be able to positionallylocate power devices 109L, 109M and 109R lateral positions to each otherand ensure that monitored or sensed parameters may be properly ascribedto each of the power devices 109L, 109M and 109R. Sensors 164 a and 164b and the other sensors of sensor interface 164 may sense electricalparameters such as DC voltage and/or current input on the DC atterminals DC+ and DC−. Sensed electrical parameter may further includethe AC the three phase voltages of the three-phase output on terminalsL1, L2 and L3. Other parameters sensed by the sensors and sensors 164 aand 164 b may include phase differences between three phase voltages onterminals L1, L2 and L3, frequencies of three phase voltages onterminals L1, L2 and L3, total harmonic distortion (THD) on three phasevoltages on terminals L1, L2 and L3, power factors of three phasevoltages on terminals L1, L2 and L3 or temperature of heatsinks and/orswitching devices utilized in power switching circuitry 160.

One or more illustrative aspects of the disclosure herein may include ageneral-purpose or special-purpose computer system including variouscomputer hardware components, which are discussed in greater detailbelow. Various aspects of the disclosure herein may also includecomputer-readable media for carrying or having computer-executableinstructions, computer-readable instructions, or data structures storedthereon. Such computer-readable media may be any available media, whichmay be accessible by a general-purpose or special-purpose computersystem. By way of example, and not limitation, such computer-readablemedia can include non-transitory computer-readable media. Suchcomputer-readable media can include physical storage media such as RAM,ROM, EPROM, flash disk, CD-ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any other media whichcan be used to carry or store desired program code mechanisms in theform of computer-executable instructions, computer-readableinstructions, or data structures and which may be accessed by ageneral-purpose or special-purpose computer system.

In this description and in the following claims, a “computer system” maybe defined as one or more software or firmware modules, one or morehardware modules, or combinations thereof, which work together toperform operations on electronic data. For example, the definition ofcomputer system may include the hardware components of a personalcomputer, as well as software or firmware modules, such as the operatingsystem of the personal computer. The physical layout of the modules maybe not important. A computer system may include one or more computersconnected via a computer network. Likewise, a computer system mayinclude a single physical device (such as a smart-phone) where internalmodules (such as a memory and processor) work together to performoperations on electronic data. While any computer system may be mobile,the term “mobile computer system” especially may include laptopcomputers, net-book computers, cellular telephones, smart-phones,wireless telephones, personal digital assistants, portable computerswith touch sensitive screens and the like.

In this description and in the following claims, a “network” may bedefined as any architecture where two or more computer systems mayexchange data. The term “network” may include wide area network,Internet local area network, Intranet, wireless networks such as“Wi-Fi”, virtual private networks, mobile access network using accesspoint name (APN) and Internet. Exchanged data may be in the form ofelectrical signals that are meaningful to the two or more computersystems. When data may be transferred, or provided over a network oranother communication connection (either hard wired, wireless, or acombination of hard wired or wireless) to a computer system or computerdevice, the connection may be properly viewed as a computer-readablemedium. Thus, any such connection may be properly termed acomputer-readable medium. Combinations of the above should also beincluded within the scope of computer-readable media.Computer-executable instructions include, for example, instructions anddata which cause a general-purpose computer system or special-purposecomputer system to perform a certain function or group of functions.

The term “server” as used herein, refers to a computer system includinga processor, data storage and a network adapter generally configured toprovide a service over the computer network. A computer system whichreceives a service provided by the server may be known as a “client”computer system. The term “data” as used herein may refer to a processedanalogue signal, the processing including analogue to digital conversioninto digital information accessible to a computer system.

It may be noted that various connections are set forth between elementsherein. These connections are described in general and, unless specifiedotherwise, may be direct or indirect; this specification may be notintended to be limiting in this respect. Further, elements of one aspectof the disclosure (and/or one case) may be combined with elements fromother aspects of the disclosure (and/or other cases) in appropriatecombinations or sub-combinations.

Aspects of the disclosure have been described in terms of examples.While illustrative systems and methods as described herein embodyingvarious aspects of the present disclosure are shown, it will beunderstood that modifications may be made by in light of the foregoingteachings. For example, each of the features of the aforementionedexamples may be utilized alone or in combination or sub-combination withelements of the other examples. For example, any of the above describedsystems and methods or parts thereof may be combined with the othermethods and systems or parts thereof described above. For example, thesteps shown in the figures may be performed in other than the recitedorder, and one or more steps shown may be optional in accordance withaspects of the disclosure. It will also be appreciated and understoodthat modifications may be made without departing from the scope of thepresent disclosure. The description is thus to be regarded asillustrative instead of restrictive on the present disclosure.

Various features are further described in the following additionalclauses:

Clause 1. An apparatus comprising:a plurality of direct current (DC) to alternating current (AC) threephase inverters connected in a parallel connection, wherein the parallelconnection includes:at least one pair of DC input terminals; anda three-phase output including a first phase, a second phase and a thirdphase provided respectively on a first phase AC output terminal, asecond phase AC output terminal and a third phase AC output terminal,wherein two of conductors of the three phases of a three-phase output ofat least one of the DC to AC three phase inverters are swapped andconnected by the three-phase output to at least one of: the first phaseAC output terminal, the second phase AC output terminal, or the thirdphase AC output terminal.Clause 2. The apparatus of clause 1, wherein the DC to AC three phaseinverters are configured to convert DC power on the at least one pair ofDC input terminals to a combined AC power on the first phase AC outputterminal, the second phase AC output terminal and the third phase ACoutput terminal.Clause 3. The apparatus of clause 1, wherein one of the three AC outputterminals of one of the DC to AC three phase inverters is connected toone of the three AC output terminals of another one of the DC to ACthree phase inverters, andwherein the one of the three AC output terminals of one of the DC to ACthree phase inverters provides a different phase compared to the one ofthe three AC output terminals of the another one of the DC to AC threephase inverters.Clause 4. The apparatus of clause 3, wherein the plurality of the DC toAC three phase inverters comprise a first DC to AC three phase inverter,a second DC to AC three phase inverter, and a third DC to AC three phaseinverter, the first DC to AC three phase inverter is laterallypositioned on the left of the second DC to AC three phase inverter, andthe third DC to AC three phase inverter is laterally positioned on theright of the second DC to AC three phase inverter.Clause 5. The apparatus of clause 4, wherein the first phase AC outputterminal of the first DC to AC three phase inverter is connected to thefirst phase AC output terminal of the second DC to AC three phaseinverter and to the first phase AC output terminal of the third DC to ACthree phase inverter,wherein the second phase AC output terminal of the first DC to AC threephase inverter is connected to the second phase AC output terminal ofthe second DC to AC three phase inverter and to the third phase ACoutput terminal of the third DC to AC three phase inverter, andwherein the third phase AC output terminal of the first DC to AC threephase inverter is connected to the third phase AC output terminal of thesecond DC to AC three phase inverter and to the second phase AC outputterminal of the third DC to AC three phase inverter.Clause 6. The apparatus of clause 5, further comprising:a first phase output that is connected to the first phase AC outputterminal of the first DC to AC three phase inverter, the first phase ACoutput terminal of the second DC to AC three phase inverter, and thefirst phase AC output terminal of the third DC to AC three phaseinverter,a second phase put that is connected to the second phase AC outputterminal of the first DC to AC three phase inverter, the second phase ACoutput terminal of the second DC to AC three phase inverter, and thethird phase AC output terminal of the third DC to AC three phaseinverter, anda third phase output that is connected to the third phase AC outputterminal of the first DC to AC three phase inverter, the third phase ACoutput terminal of the second DC to AC three phase inverter, and thesecond phase AC output terminal of the third DC to AC three phaseinverter.Clause 7. The apparatus of clause 4, wherein the first phase AC outputterminal of the first DC to AC three phase inverter is connected to thesecond phase AC output terminal of the second DC to AC three phaseinverter and to the second phase AC output terminal of the third DC toAC three phase inverter,wherein the second phase AC output terminal of the first DC to AC threephase inverter is connected to the third phase AC output terminal of thesecond DC to AC three phase inverter and to the first phase AC outputterminal of the third DC to AC three phase inverter, andwherein the third phase AC output terminal of the first DC to AC threephase inverter is connected to the first phase AC output terminal of thesecond DC to AC three phase inverter and to the third phase AC outputterminal of the third DC to AC three phase inverter.Clause 8. The apparatus of clause 7, further comprising:a first phase output that is connected to the second phase AC outputterminal of the first DC to AC three phase inverter, the third phase ACoutput terminal of the second DC to AC three phase inverter, and thefirst phase AC output terminal of the third DC to AC three phaseinverter,a second phase put that is connected to the third phase AC outputterminal of the first DC to AC three phase inverter, the first phase ACoutput terminal of the second DC to AC three phase inverter, and thethird phase AC output terminal of the third DC to AC three phaseinverter, anda third phase output that is connected to the first phase AC outputterminal of the first DC to AC three phase inverter, the second phase ACoutput terminal of the second DC to AC three phase inverter, and thesecond phase AC output terminal of the third DC to AC three phaseinverter.Clause 9. A method for a plurality of direct current (DC) to alternatingcurrent (AC) three phase inverters connected in a parallel connection,the method comprising:mounting and positioning the DC to AC three phase inverters, wherein atleast one of the DC to AC three phase inverters is laterally positionedto the left or to the right of another DC to AC three phase inverters;providing for the parallel connection between at least one pair of DCinput terminals and a three-phase output including a first phase, asecond phase and a third phase provided respectively on a first phase ACoutput terminal, a second phase AC output terminal and a third phase ACoutput terminal; andin the parallel connection, swapping and connecting two conductors ofthe three phases of a three-phase output of at least one of the DC to ACthree phase inverters to at least one of: the first phase AC outputterminal, the second phase AC output terminal, or the third phase ACoutput terminal.Clause 10. The method of clause 9, wherein the swapping and connectingcomprises:connecting one of the three AC output terminals of one of the DC to ACthree phase inverters is connected to one of the three AC outputterminals of another one of the DC to AC three phase inverters,wherein the one of the three AC output terminals of one of the DC to ACthree phase inverters provides a different phase compared to the one ofthe three AC output terminals of the another one of the DC to AC threephase inverters.Clause 11. The method of clause 9, further comprising:converting DC power on the at least one pair of DC input terminals to acombined AC power on the first phase AC output terminal, the secondphase AC output terminal and the third phase AC output terminal;sensing a parameter on at least one of: the first phase AC outputterminal, the second phase AC output terminal, or the third phase ACoutput terminal; andverifying, responsive to the sensing and the mounting, the lateralpositioning of the DC to AC three phase inverters to each other.Clause 12. The method of clause 9, clause 10, or clause 11 furthercomprising:providing an auxiliary power to each the DC to AC three phase invertersfrom at least one of: the first phase AC output terminal and a neutralterminal, the second phase AC output terminal and the neutral terminal,or the third phase AC output terminal and the neutral terminal.Clause 13. The method of clause 11 or clause 12, wherein the parameteris selected from at least one of: voltage, current, frequency phaseangle, power factor, impedance, harmonic distortion or temperature.Clause 14. The method of clause 9, wherein the plurality of the DC to ACthree phase inverters comprise a first DC to AC three phase inverter, asecond DC to AC three phase inverter, and a third DC to AC three phaseinverter, the first DC to AC three phase inverter is laterallypositioned on the left of the second DC to AC three phase inverter, andthe third DC to AC three phase inverter is laterally positioned on theright of the second DC to AC three phase inverter.Clause 15. The method of clause 14, further comprising:connecting the first phase AC output terminal of the first DC to ACthree phase inverter to the first phase AC output terminal of the secondDC to AC three phase inverter and to the first phase AC output terminalof the third DC to AC three phase inverter,connecting the second phase AC output terminal of the first DC to ACthree phase inverter to the second phase AC output terminal of thesecond DC to AC three phase inverter and to the third phase AC outputterminal of the third DC to AC three phase inverter, andconnecting the third phase AC output terminal of the first DC to ACthree phase inverter to the third phase AC output terminal of the secondDC to AC three phase inverter and to the second phase AC output terminalof the third DC to AC three phase inverter.Clause 16. The method of clause 15, further comprising:connecting a first phase output to the first phase AC output terminal ofthe first DC to AC three phase inverter, the first phase AC outputterminal of the second DC to AC three phase inverter, and the firstphase AC output terminal of the third DC to AC three phase inverter,connecting a second phase put to the second phase AC output terminal ofthe first DC to AC three phase inverter, the second phase AC outputterminal of the second DC to AC three phase inverter, and the thirdphase AC output terminal of the third DC to AC three phase inverter, andconnecting a third phase output to the third phase AC output terminal ofthe first DC to AC three phase inverter, the third phase AC outputterminal of the second DC to AC three phase inverter, and the secondphase AC output terminal of the third DC to AC three phase inverter.Clause 17. The method of clause 14, further comprising:connecting the first phase AC output terminal of the first DC to ACthree phase inverter to the second phase AC output terminal of thesecond DC to AC three phase inverter and to the second phase AC outputterminal of the third DC to AC three phase inverter,connecting the second phase AC output terminal of the first DC to ACthree phase inverter to the third phase AC output terminal of the secondDC to AC three phase inverter and to the first phase AC output terminalof the third DC to AC three phase inverter, andconnecting the third phase AC output terminal of the first DC to ACthree phase inverter to the first phase AC output terminal of the secondDC to AC three phase inverter and to the third phase AC output terminalof the third DC to AC three phase inverter.Clause 18. The method of clause 17, further comprising:connecting a first phase output to the second phase AC output terminalof the first DC to AC three phase inverter, the third phase AC outputterminal of the second DC to AC three phase inverter, and the firstphase AC output terminal of the third DC to AC three phase inverter,connecting a second phase put to the third phase AC output terminal ofthe first DC to AC three phase inverter, the first phase AC outputterminal of the second DC to AC three phase inverter, and the thirdphase AC output terminal of the third DC to AC three phase inverter, andconnecting a third phase output to the first phase AC output terminal ofthe first DC to AC three phase inverter, the second phase AC outputterminal of the second DC to AC three phase inverter, and the secondphase AC output terminal of the third DC to AC three phase inverter.Clause 19. A non-transitory computer readable medium having program coderecorded thereon which, when executed by one or more processors, causesthe one or more processors to:sense with a sensor at least one phase difference between at least twophases of a group of parallel connected 3 phase AC output terminals,wherein the parallel connected AC output terminals are three parallelconnected DC to AC three phase inverters, wherein the 3 phase AC outputterminals are selected from a group comprising of at least one of: afirst phase AC output terminal, a second phase AC output terminal, or athird phase AC output terminal, wherein wiring of conductors to at leastone phase of an AC output terminal is swapped by the AC output terminalswith wiring of conductors of at least one phase of another phase ACoutput terminal; andverify that a sign of at least one phase difference is different tosigns of other phase differences to determine a lateral position of atleast one three phase inverters relative to at least one other of thethree phase inverters.Clause 20. The non-transitory computer readable medium of clause 19,wherein the program code, when executed by the one or more processors,further causes the one or more processors to:connect one of the 3 phase AC output terminals of one of the DC to ACthree phase inverters is connected to one of the 3 phase AC outputterminals of another one of the DC to AC three phase inverters,wherein the one of the 3 phase AC output terminals of one of the DC toAC three phase inverters provides a different phase compared to the oneof the 3 phase AC output terminals of the another one of the DC to ACthree phase inverters.Clause 21. An apparatus comprising:a first set of input terminals, a second set of input terminals and athird set of input terminals, wherein each set of input terminalscomprises a first phase input terminal, a second phase input terminaland a third phase input terminal, and the first, second and third inputterminals are labeled as first, second and third terminals,respectively; and a set of output terminals comprising a first phaseoutput terminal, a second phase output terminal and a third phase outputterminal,wherein the first phase input terminal of the first set of inputterminals is connected to the first phase input terminal of the secondset of input terminals, the first phase input terminal of the third setof input terminals and to the first phase output,wherein the second phase input terminal of the first set of inputterminals is connected to the second phase input terminal of the secondset of input terminals, the third phase input terminal of the third setof input terminals and to the second phase output, andwherein the third phase input terminal of the first set of inputterminals is connected to the third phase input terminal of the secondset of input terminals, the second phase input terminal of the third setof input terminals and to the third phase output.Clause 22. The apparatus of clause 21, wherein the first, second andthird input terminals are labeled as first, second and third terminals,respectively, using alphanumeric characters.Clause 23. The apparatus of clause 21 or clause 22, wherein the first,second and third input terminals are labeled as first, second and thirdterminals, respectively, using a first color to label the first inputterminal, a second color to label the second input terminal and a thirdcolor to label the third input terminal.Clause 24. An apparatus comprising:a first set of input terminals, a second set of input terminals and athird set of input terminals, wherein each set of input terminalscomprises a first phase input terminal, a second phase input terminaland a third phase input terminal, and the first, second and third inputterminals are labeled as first, second and third terminals,respectively; anda set of output terminals comprising a first phase output terminal, asecond phase output terminal and a third phase output terminal,wherein the first phase input terminal of the first set of inputterminals is connected to the second phase input terminal of the secondset of input terminals, the second phase input terminal of the third setof input terminals and to the third phase output,wherein the second phase input terminal of the first set of inputterminals is connected to the third phase input terminal of the secondset of input terminals, the first phase input terminal of the third setof input terminals and to the first phase output; andwherein the third phase input terminal of the first set of inputterminals is connected to the first phase input terminal of the secondset of input terminals, the third phase input terminal of the third setof input terminals and to the second phase output.Clause 25. The apparatus of clause 24, wherein the first phase inputterminal of each of the first set of input terminals, the second set ofinput terminals and the third set of input terminals is connected to arespective auxiliary power circuit.Clause 26. A method comprising:connecting output terminals of three DC/AC three-phase converters inparallel,creating a combined three-phase AC output,drawing power from a first phase of the three-phase AC output to provideauxiliary power to a first DC/AC converter,drawing power from a second phase of the three-phase AC output toprovide auxiliary power to a second DC/AC converter, anddrawing power from a third phase of the three-phase AC output to provideauxiliary power to a third DC/AC converter.Clause 27. The method of clause 26, wherein connecting output terminalsof three DC/AC three-phase converters in parallel comprises:connecting each of a first labeled phase terminal, a second labeledphase terminal and a third labeled phase terminal to a correspondinglylabeled terminal.Clause 28. The method of clause 26 or clause 27, wherein the three DC/ACthree phase converters draw auxiliary power from substantiallyidentically-labeled phases.

What is claimed is:
 1. An apparatus comprising: a plurality of directcurrent (DC) to alternating current (AC) three phase inverters connectedin a parallel connection, wherein the parallel connection includes: atleast one pair of DC input terminals; and a three-phase output includinga first phase, a second phase and a third phase provided respectively ona first phase AC output terminal, a second phase AC output terminal anda third phase AC output terminal, wherein two of conductors of the threephases of a three-phase output of at least one of the DC to AC threephase inverters are swapped and connected by the three-phase output toat least one of: the first phase AC output terminal, the second phase ACoutput terminal, or the third phase AC output terminal.
 2. The apparatusof claim 1, wherein the DC to AC three phase inverters are configured toconvert DC power on the at least one pair of DC input terminals to acombined AC power on the first phase AC output terminal, the secondphase AC output terminal and the third phase AC output terminal.
 3. Theapparatus of claim 1, wherein one of the three AC output terminals ofone of the DC to AC three phase inverters is connected to one of thethree AC output terminals of another one of the DC to AC three phaseinverters, and wherein the one of the three AC output terminals of oneof the DC to AC three phase inverters provides a different phasecompared to the one of the three AC output terminals of the another oneof the DC to AC three phase inverters.
 4. The apparatus of claim 3,wherein the plurality of the DC to AC three phase inverters comprise afirst DC to AC three phase inverter, a second DC to AC three phaseinverter, and a third DC to AC three phase inverter, the first DC to ACthree phase inverter is laterally positioned on the left of the secondDC to AC three phase inverter, and the third DC to AC three phaseinverter is laterally positioned on the right of the second DC to ACthree phase inverter.
 5. The apparatus of claim 4, wherein the firstphase AC output terminal of the first DC to AC three phase inverter isconnected to the first phase AC output terminal of the second DC to ACthree phase inverter and to the first phase AC output terminal of thethird DC to AC three phase inverter, wherein the second phase AC outputterminal of the first DC to AC three phase inverter is connected to thesecond phase AC output terminal of the second DC to AC three phaseinverter and to the third phase AC output terminal of the third DC to ACthree phase inverter, and wherein the third phase AC output terminal ofthe first DC to AC three phase inverter is connected to the third phaseAC output terminal of the second DC to AC three phase inverter and tothe second phase AC output terminal of the third DC to AC three phaseinverter.
 6. The apparatus of claim 5, further comprising: a first phaseoutput that is connected to the first phase AC output terminal of thefirst DC to AC three phase inverter, the first phase AC output terminalof the second DC to AC three phase inverter, and the first phase ACoutput terminal of the third DC to AC three phase inverter, a secondphase put that is connected to the second phase AC output terminal ofthe first DC to AC three phase inverter, the second phase AC outputterminal of the second DC to AC three phase inverter, and the thirdphase AC output terminal of the third DC to AC three phase inverter, anda third phase output that is connected to the third phase AC outputterminal of the first DC to AC three phase inverter, the third phase ACoutput terminal of the second DC to AC three phase inverter, and thesecond phase AC output terminal of the third DC to AC three phaseinverter.
 7. The apparatus of claim 4, wherein the first phase AC outputterminal of the first DC to AC three phase inverter is connected to thesecond phase AC output terminal of the second DC to AC three phaseinverter and to the second phase AC output terminal of the third DC toAC three phase inverter, wherein the second phase AC output terminal ofthe first DC to AC three phase inverter is connected to the third phaseAC output terminal of the second DC to AC three phase inverter and tothe first phase AC output terminal of the third DC to AC three phaseinverter, and wherein the third phase AC output terminal of the first DCto AC three phase inverter is connected to the first phase AC outputterminal of the second DC to AC three phase inverter and to the thirdphase AC output terminal of the third DC to AC three phase inverter. 8.The apparatus of claim 7, further comprising: a first phase output thatis connected to the second phase AC output terminal of the first DC toAC three phase inverter, the third phase AC output terminal of thesecond DC to AC three phase inverter, and the first phase AC outputterminal of the third DC to AC three phase inverter, a second phase putthat is connected to the third phase AC output terminal of the first DCto AC three phase inverter, the first phase AC output terminal of thesecond DC to AC three phase inverter, and the third phase AC outputterminal of the third DC to AC three phase inverter, and a third phaseoutput that is connected to the first phase AC output terminal of thefirst DC to AC three phase inverter, the second phase AC output terminalof the second DC to AC three phase inverter, and the second phase ACoutput terminal of the third DC to AC three phase inverter.
 9. A methodfor a plurality of direct current (DC) to alternating current (AC) threephase inverters connected in a parallel connection, the methodcomprising: mounting and positioning the DC to AC three phase inverters,wherein at least one of the DC to AC three phase inverters is laterallypositioned to the left or to the right of another DC to AC three phaseinverters; providing for the parallel connection between at least onepair of DC input terminals and a three-phase output including a firstphase, a second phase and a third phase provided respectively on a firstphase AC output terminal, a second phase AC output terminal and a thirdphase AC output terminal; and in the parallel connection, swapping andconnecting two conductors of the three phases of a three-phase output ofat least one of the DC to AC three phase inverters to at least one of:the first phase AC output terminal, the second phase AC output terminal,or the third phase AC output terminal.
 10. The method of claim 9,wherein the swapping and connecting comprises: connecting one of thethree AC output terminals of one of the DC to AC three phase invertersis connected to one of the three AC output terminals of another one ofthe DC to AC three phase inverters, wherein the one of the three ACoutput terminals of one of the DC to AC three phase inverters provides adifferent phase compared to the one of the three AC output terminals ofthe another one of the DC to AC three phase inverters.
 11. The method ofclaim 9, further comprising: converting DC power on the at least onepair of DC input terminals to a combined AC power on the first phase ACoutput terminal, the second phase AC output terminal and the third phaseAC output terminal; sensing a parameter on at least one of: the firstphase AC output terminal, the second phase AC output terminal, or thethird phase AC output terminal; and verifying, responsive to the sensingand the mounting, the lateral positioning of the DC to AC three phaseinverters to each other.
 12. The method of claim 9 further comprising:providing an auxiliary power to each the DC to AC three phase invertersfrom at least one of: the first phase AC output terminal and a neutralterminal, the second phase AC output terminal and the neutral terminal,or the third phase AC output terminal and the neutral terminal.
 13. Themethod of claim 11, wherein the parameter is selected from at least oneof: voltage, current, frequency phase angle, power factor, impedance,harmonic distortion or temperature.
 14. The method of claim 9, whereinthe plurality of the DC to AC three phase inverters comprise a first DCto AC three phase inverter, a second DC to AC three phase inverter, anda third DC to AC three phase inverter, the first DC to AC three phaseinverter is laterally positioned on the left of the second DC to ACthree phase inverter, and the third DC to AC three phase inverter islaterally positioned on the right of the second DC to AC three phaseinverter.
 15. The method of claim 14, further comprising: connecting thefirst phase AC output terminal of the first DC to AC three phaseinverter to the first phase AC output terminal of the second DC to ACthree phase inverter and to the first phase AC output terminal of thethird DC to AC three phase inverter, connecting the second phase ACoutput terminal of the first DC to AC three phase inverter to the secondphase AC output terminal of the second DC to AC three phase inverter andto the third phase AC output terminal of the third DC to AC three phaseinverter, and connecting the third phase AC output terminal of the firstDC to AC three phase inverter to the third phase AC output terminal ofthe second DC to AC three phase inverter and to the second phase ACoutput terminal of the third DC to AC three phase inverter.
 16. Themethod of claim 15, further comprising: connecting a first phase outputto the first phase AC output terminal of the first DC to AC three phaseinverter, the first phase AC output terminal of the second DC to ACthree phase inverter, and the first phase AC output terminal of thethird DC to AC three phase inverter, connecting a second phase put tothe second phase AC output terminal of the first DC to AC three phaseinverter, the second phase AC output terminal of the second DC to ACthree phase inverter, and the third phase AC output terminal of thethird DC to AC three phase inverter, and connecting a third phase outputto the third phase AC output terminal of the first DC to AC three phaseinverter, the third phase AC output terminal of the second DC to ACthree phase inverter, and the second phase AC output terminal of thethird DC to AC three phase inverter.
 17. The method of claim 14, furthercomprising: connecting the first phase AC output terminal of the firstDC to AC three phase inverter to the second phase AC output terminal ofthe second DC to AC three phase inverter and to the second phase ACoutput terminal of the third DC to AC three phase inverter, connectingthe second phase AC output terminal of the first DC to AC three phaseinverter to the third phase AC output terminal of the second DC to ACthree phase inverter and to the first phase AC output terminal of thethird DC to AC three phase inverter, and connecting the third phase ACoutput terminal of the first DC to AC three phase inverter to the firstphase AC output terminal of the second DC to AC three phase inverter andto the third phase AC output terminal of the third DC to AC three phaseinverter.
 18. The method of claim 17, further comprising: connecting afirst phase output to the second phase AC output terminal of the firstDC to AC three phase inverter, the third phase AC output terminal of thesecond DC to AC three phase inverter, and the first phase AC outputterminal of the third DC to AC three phase inverter, connecting a secondphase put to the third phase AC output terminal of the first DC to ACthree phase inverter, the first phase AC output terminal of the secondDC to AC three phase inverter, and the third phase AC output terminal ofthe third DC to AC three phase inverter, and connecting a third phaseoutput to the first phase AC output terminal of the first DC to AC threephase inverter, the second phase AC output terminal of the second DC toAC three phase inverter, and the second phase AC output terminal of thethird DC to AC three phase inverter.
 19. A non-transitory computerreadable medium having program code recorded thereon which, whenexecuted by one or more processors, causes the one or more processorsto: sense with a sensor at least one phase difference between at leasttwo phases of a group of parallel connected 3 phase AC output terminals,wherein the parallel connected AC output terminals are three parallelconnected DC to AC three phase inverters, wherein the 3 phase AC outputterminals are selected from a group comprising of at least one of: afirst phase AC output terminal, a second phase AC output terminal, or athird phase AC output terminal, wherein wiring of conductors to at leastone phase of an AC output terminal is swapped by the AC output terminalswith wiring of conductors of at least one phase of another phase ACoutput terminal; and verify that a sign of at least one phase differenceis different to signs of other phase differences to determine a lateralposition of at least one three phase inverters relative to at least oneother of the three phase inverters.
 20. The non-transitory computerreadable medium of claim 19, wherein the program code, when executed bythe one or more processors, further causes the one or more processorsto: connect one of the 3 phase AC output terminals of one of the DC toAC three phase inverters is connected to one of the 3 phase AC outputterminals of another one of the DC to AC three phase inverters, whereinthe one of the 3 phase AC output terminals of one of the DC to AC threephase inverters provides a different phase compared to the one of the 3phase AC output terminals of the another one of the DC to AC three phaseinverters.